Casting mold and method of making same



Dec. 20, 1927. 1,653,344

M. CLAWSON CASTING MOLD AND METHOD OF MAKING SAME Filed April 1921 givwcwkw Patented Dec. 20, 1927.

UNITED STATES 1,653,344 PATENT OFFICE.

MONROE S. GIiAWSON, OF UPPER HONTGLAR NEW JERSEY.

CASTING MOLD AND METHOD IAKING" Application filed A ril 7, 1921 serial in. 459,318.

This invention relates to the metallurgical art, particularly to molds and casting processes, and has for its object theprovlsion of a novel mold adapted for use in the casting of high speed steels and other metals, and particularly those alloys that are read ily oxi'dizable, the mold being of such a nature as to withstand the very high temperatures necessary in the fusing of such metals or alloys without breaking down, the

mold being furthermore of such a nature as to be very porous-so that when used in carrying out my process which involves the application of suction upon the mold or impression, the gases generated at the surface of contact of the molten material with the mold will be drawn ofi? in order to prevent the formation of blisters, air holes, and what is known in the art as minus material.

An important object is the provision of a mold of this character consisting of high refractory material containing an excess of oil or varnish whereby to present a smooth molding surface to the molten metal while retaining sufficient porosit to facilitate the exhaust or drawing off 0 the gases generated when the metal is .poured, the mold being also of such a tenacious formation as to permit machining thereof whereby to define a sharp-impression when the metal is cast therein.

I am aware that the art of casting with suction applied to the mold is not broadly new and I am also aware that oil and sand I the oil being either of a mineral or vegetable type. I am also aware that certain of the ingredients which I employ in the composition of my mold have been used before in the same art but-heretofore it has apparently been impossible to make a mold containing oil adapted for use in casting high speed steels or other alloys containing magnesium, tungsten or other readily oxidizable metals owing to the fact that the molds known and used break up when subjected to exposure to the high temperatures necessary to the fusing of such alloys. Such well known molds either disintegrate to a greater or lessextent and cause rough castings or else the oil used as a binder gasifies to such an extent as to cause too great a number of blow holes, blisters and the like which render the casting practically Worthless.

It is to avoid the above mentioned objections that the present invention has been dehave been used in the formation of molds,-

signed, this invention insuring the produe isused is mixed with a fatty or hydrocarbon binder such as a dryin oil or varnish, the pro ortions of oxide an binder varying under ifierent conditions though it is necessary tov use what I may term an excess of the oil or varnish. The impression is made in this mass in the customary manner and the mold is then baked by suitable means and at a suitable temperature to render it solid. H

The exact length of time during which the mold is baked may of course vary,.depending upon the proportion of oxide and drying material, and also de ending upon the temperature and other con itions. However, the intention is to discontinue thebaking before the mold becomes dry and brittle. If an excess of oil or otherdrying materi a1 is used the baking may be contmued for as long a time as ordinary molds are baked but would still retain suflicient of the oil to be very slightly plastic, in the sense of being indentable if struck by a hard object though not being brittle or friable. The mold is, however, porous so as to permit suction through it. The condition is of course sufliciently hard to prevent any possible distortion when molten metal is poured into the mold. It is intended that suflicient .oil remain in the mold after the baking operation to necessitate suction for carr mg off the gases formed by the burning o the oil when the metal impinges agamst the mold.

In carrying out the process it is of course necessary to provide some apparatus in which suction may be applied to the mold. Such an apparatus is conventionally illustrated in the drawing which shows a longitudinal sectional view through a suitable holder or receptacle 10, naturally of refractory material, provided at its bottom with an outlet tube 11 to which suction is applied by any suitable means such as an air pump or the like, not shown. The mold or impression, designated by the numeral 12, which is formed from the above described mass, is

12 suction is applied to the tube 11 so that the gases generated'by the burning or CllS- integration of the excess oil in the mold may be sucked out through the pores of the mold whereby to prevent the formation of air holes, blisters, and the like in the, resultant casting 13 and to insure the drawing of the molten metal into even the smallest indentations in the mold. This will insure a sharp casting.

It .will be noted that there is no intention of rarefying' the air within .themold holder or receptacle, but that absolute 1y direct suction through the mold is roduced to carry away or exhaust the hy rocarbon, carbon monoxide and oxy-hydrogen gases caused by the disintegration of the binder at the surface of contact of the molten metal with the mold. It is strictly the diaphragm-like nature of the mold which permits this action.

In actual practice I have discovered that a mold constructed of the above mentioned materials and treated as described, is not only capable of being carved or machined to produce sharp impressions but is also capable of withstandin the high temperatures necessary to cause using of the many alloys incapable of being properly cast with the ordinary apparatus and in the ordinary processes. -I have ascertained from experiment that with my mold and process it is possible to cast alloys of steel, nickel, cobalt, and the like 'inintricate shapes to almost exact size.

In my process I entirely avoid the formation what is known in the art as a skin on the surface of the casting unlike the internal structure of the metal itself, such skin being caused by the burning in of some of the molding material and the chilling caused by the binder used to manitain the shape of the article to be cast. In casting alloys requiring a high temperature to effect melting thereof, the ordinary mold materials such as plaster of Paris depending upon water of crystallization, are unsuitable as such a mold breaks down at a low temperature. In in mold, however, I have discovered that al the above enumerated dis-.

advantages have been eliminated so that almost perfect castings of substantially exact size can be easily roduced.

"While I have s own and described the preferred embodiment of my invention, it is of course to be understood that I reserve the right to make such changes in the form, construction and arrangement of parts as will i :the mold whereby to necessitate-suction dur' .ing casting for removing mixed gases formedby the disintegration of the oil u on impingementof molten metal against the mold.

2. The method of making a mold consisting in mixing together a' mineral oxide and a fluent drying material, baking the mold to substantialihardness and discontinuing the baking at a point where suflicient fluent drying material remains in the mold to imparta slight but appreciable plasticity thereto and to require suction during casting. 3. The method of making a mold, consistingi in mixing together a metallic oxide and a rying oil, making the impression in the mass, and-baking the mold to expel the major portion of the oil and to bring about sub- ,stantial hardness and porosity, the baking being discontinued at a point where sufiicient oil remains in the moldto necessitate suction durin casting.

4. mold consisting of a mineral oxide and a fluent drying material treated to possess machineable hardness and to retain a suificient quantity of the drying material after treatment to possessmalleability.

5. A mold comprising a mineral oxide and a resinous drying material of fluent character, the mold being baked to machineable hardness, and having suflicient drying material remaining after treatment to render it malleable and to require suction during casting for the carrying off of gases caused by disintegration of the drying material.

In testimony whereof I hereto afiix my signature.

MONROE S. CLAWSON. 

